Development and Evaluation of the Quintessential Ventricular Cannula

Left Ventricular Assist Devices (LVADs) are becoming a more widely accepted form of treatment for patients suffering from end stage heart failure. First generation LVADs attempted to mimic the physiology of the native heart by generating pulsatile blood flow. Second- and third-generation turbodynamic LVADs are much smaller than pulsatile LVADs, but alternatively generate non-physiologic continuous flow.A vast amount of time and resources have been spent on optimizing the hemodynamics LVADs. One area that has changed very little, however, is the apical cannula- an inflow conduit that is inserted into the apex of the left ventricle (LV) allowing blood to be drawn from the LV chamber by the LVAD so that the heart can be effectively unloaded. Current inflow cannulae are often straight rigid tubes which extend far into the LV, and are susceptible to becoming displaced during the implantation of the device or post-operatively. A malpositioned cannula may cause reduced flow, it may interfere with ventricular anatomy, and it may generate areas of stagnation that can form thrombus. Additionally, the advent of continuous flow LVADs brought about a new problem where the negative pressures generated within the ventricle by the LVAD can cause the chamber to collapse. A sub-optimally placed cannula may increase the likelihood of these suction events.An ongoing collaborative effort at the University of Pittsburgh and Carnegie Mellon University has resulted in the design of a more robust low-profile cannula. The design is intended to minimize variations in pump output by reducing the cannula's ability to be malpositioned. This reduces interactions with ventricular anatomy, and is more likely to generate hemodynamically favorable flow. This design is also intended to reduce the likelihood of ventricular collapse across the spectrum of physiologic conditions by providing mechanical support for the ventricular wall.In-silico and ex-vivo studies, including in-situ visualization of ventricular suction in an arrested ovine ventricle, demonstrated that the novel cannula design is indeed a more robust design, and more compatible with ventricular anatomy. Further development of the flared inflow cannula is warranted, as is the study of its interaction with the left ventricle under sub-optimal conditions